Use of condoms isn't always a "need" thing" sometimes it is just something someone wants, rather than needs.
So, when a partner uses a condom is going to be about when you WANT them to use one.
However, I would suggest that if you are having a ton of anxiety around pregnancy with activities like manual sex that don't present that risk realistically, you might instead want to take some time away from sex of any kind, including this kind, that does get you all freaked out to figure out what you need to feel comfortable having sex without a ton of worry.
It might be that this is just too soon for you, period. It might be that you don't feel safe with your partner, or that you're actually enjoying anything enough to do anything but worry. maybe you are doing things only because you feel you have to. Maybe it just all feels too risky in the context of your life right now, so the timing is off. Have you thought about any of this in that kind of evaluative way?
Never doubt that a small group of thoughtful, committed citizens can change the world. Indeed, it is the only thing that ever has. - Margaret Mead